The following describes a liquid collecting apparatus taking a blood collecting apparatus that collects blood as one example. The blood collecting apparatus is used for quantitative analyses in nuclear medicine diagnosis (e.g., PET (Positron Emission Tomography)) and so on. In the nuclear medicine diagnosis, the quantitative analyses of information on a vital function, such as concentrations of nerve receptors and metabolism of tumor, require measurement of a time variation in agent concentration of plasma in arterial blood, i.e., a radioactive concentration. The following modes are adopted in an automatic blood collecting apparatus for measuring a radioactive concentration in blood. See, for example, Patent Literatures 1 and 2, and Non-Patent Literatures 1 and 2. The apparatus are used for measuring a radioactive concentration in arterial blood of small animals (e.g., mice, rats and so on). It should be noted that the automatic blood collecting apparatus in Patent Literature 1 differs from those in the other modes in purpose of use.
[Non-Patent Literature 1] In Non-Patent Literature 1, a radiation detector is installed to sandwich a part of a catheter inserted into arteria to measure a radioactive concentration in blood. An elongated diode has a length of 30 [mm] A tube containing blood is arranged along a long side of the diode, causing an increased detectable area. This achieves ensured detection efficiency of β+-rays. The catheter includes one end connected to a syringe pump. The catheter pulls the syringe pump at a certain rate to draw blood. A flow rate of blood is calculated from the rate and a volume of blood is calculated from an internal diameter of the catheter, whereby a radioactive concentration is measured.
[Non-Patent Literature 2] As illustrated FIG. 7 in Non-Patent Literature 2, blood is returned into the vein V from the end of catheter C inserted into the arteria A. A LYSO detector D and a Perista pump P are installed in a part of the catheter C. β+-rays in the arterial blood flowing inside the interior catheter C are annihilated to generate γ-rays. The γ-rays enter into the LYSO detector D to emit light, and the number of optical fibers F is counted with the light in a collecting box B. The Perista pump P controls a flow rate of blood. A control PC calculates a volume of blood from the flow rate and the internal diameter of the catheter, thereby measuring a radioactive concentration.
[Patent Literature 1] A flow path is switched by a five-way joint to repeat ejection of blood or a cleaning liquid and collection of blood.
[Patent Literature 2] The present application has suggested a technique concerning the automatic blood collecting apparatus. Patent Literature 2 discloses a process of pushing back blood into an animal using physiological saline solution containing heparin.